A activated anionic lactam polymerization is generally performed by the separate addition of a catalyst and an activator to the lactam melt, wherein the so-called two-pot method has gained acceptance in connection with many applications. Here, melt portions of equal volume are prepared, in which either a catalyst or an activator has been dissolved. These melts are combined for the accelerated initiation of the polymerization. Therefore the method requires two separate melt tanks for lactams containing dissolved substances, such as catalyst or activator, which are active at higher temperatures. Therefore the storage stability of the melts is significantly reduced.
The polymerization of lactam could be greatly simplified and more universally applied if it were possible to omit the provision of the lactam melt, respectively containing a dissolved catalyst and a dissolved activator, whereby its storage ability is reduced. This applies in particular to lactam-12, which only becomes liquid above 150.degree. C.
The situation is further complicated by the fact that catalyst and activator must be supplied separately to the lactam melt. Thereby the catalyst generally is a solid, and many activators are also solids, so that polymerization must always be preceded by separate dissolving processes, during which the polymerization of the lactam can already start. This applies in particular to lactam-12 with its high melting point and the introduction of catalyst into the lactam melt.
If a catalyst containing lactam-6 is used for the polymerization of other lactams, copolymerisation occurs, although only in small amounts.
Since known catalysts for lactam polymerization are solids with a limited storage life, which for their use require a dissolving process in previously melted lactam, complicated solvent systems have been developed for making available a catalyst solution which is usable at least over a limited period of time, has a low slag formation tendency and preferably is liquid at room temperature. Examples for this are German Patent DE 22 30 732 C3 and European Patent EP 0 438 762 B1. However, even with these catalyst solutions being made available, the main disadvantage of the method remains, namely that the activator and the catalyst must respectively be added separately to the lactam melt for a fast and predetermable activated anionic lactam polymerization.
Thus there is a proven requirement to considerably simplify the activated anionic lactam polymerization, to make it more secure in its technical feasibility and to perform it with fewer process steps.
The supply of a storagestable liquid system, which contains only a little or no free lactam, which directly initiates the activated anionic lactam polymerization and permits it to take place in a discontinuous or a continuous process, would represent a very important technical progress.